Plywood Thickness

[Mike Goetzke]

I have to vent....In my spare time I'm building a cabinet for under my TS wing. I bought two sheets of oak-ply for the cabinet. I was milling some walnut I have at the surface planer for some contrasting edge banding.

I was proud of myself - I planed the stock 0.002" thicker than the ply (so I thought). I went to apply it and discovered it was too thin. By almost 0.020"! Took me a while to figure it out, but, it ends up the two sheets of ply were different in thickness. I bought them at the same time from the same rack. Guess I'll have to take my calipers to Menard's next time.

[ron hill]

Mike,
I've had the same thing happen to me trying to use Menards plywood. I once cut test dadoes and checked them against the plywood, got a nice fit and began cutting dadoes for everything else. When I tried dry fitting I had sloppy fits everywhere. Now I don't buy any plywood from them unless I'm really in a bind and then I'll get the veneered MDF which is much more uniform in thickness but not fun to work with. I recently bought several sheets of a composite core plywood and will be using them in a computer desk. I haven't checked them with a micrometer yet but will before I start. I bought this stuff from a mill in MN and they told me it was very uniform in thickness and wouldn't telegraph when using biscuits. We'll see. Ron H

[Jim Becker]

This is not unusual these days...you really need to check the stock before you cut grooves, rabbits and dados, too. One solution for cabinetry is to start using MDF core veneer sheet goods. Heavier, but very consistant in thickness. Of course, you can buy that stuff at the 'borg...you need a real plywood supplier.

[glenn bradley]

I've had the same experience as have many. Ply from the same bundle will vary. You could take your mic to the yard and fish through to get two pieces that are close but I bet they'll vary even across the length of the sheet. I try to get sheets that are reasonably close and then basically 'custom' fit as I build checking not only the general thickness but, the thickness where it will effect the joint. I find it easier to adapt the the variance than to try to find perfection in an imperfect world ;-)

[Jeffrey Makiel]

I posted a thread about two weeks ago complaining about the quality of plywood offered by the large retail home improvement stores. From the replies I received, it seems the Chinese have no lack of plywood mills that make low quality stuff...and the big retailers have no shame.

One suggestion is to look for plywood manufactured in either USA or Canada. However, I notice many of the plywoods at the big box stores don't identify their origin. Another suggestion is to look for a 3rd party stamp that states it conforms to some basic level of quality.

-Jeff :)

[Jake Helmboldt]

I don't know that the Northa American stuff is always better. I got some maple ply for recessed panels that was seriously undersized (plywood router bits were still to wide) and some of the glue seams were really poor when dye was applied they popped out like a sore thumb.

I don't know that it was US/Canadian, but it was from the local plywood supplier that is supposed to have the best sheetgoods, not Home Despot.

[Hoa Dinh]

I think plywood thickness variation is just another fact of life. I just learn to live with it.

I mimimize the use of "thickness picky" joineries (dado, rabbet). I use pocket hole and/or biscuit instead. If I have to use dado or rabbett, I use one of the jigs that use the actual material as spacer.

I try to cut similar pieces of a project from the same sheet of plywood. For example, the two sides of the bookcase come from one sheet, and all the shelves from one sheet.

For edge banding, I make the edging thicker than the plywood (how much thicker doesn't really matter), then flush trim the edging.

I choose plywood base on appearance (the outer veneer plies), amount of void, and flatness. I don't even measure the thickness anymore.

[Dan Forman]

One thing you can do is go to the extra work of cutting a rabbet in the piece you want to fit into the dado. So with 3/4" ply you cut a 1/2" dado, then cut a rabbet which leaves 1/2" on the edge of the piece to go into the dado.

Dan